title: AKT3 controls mitochondrial biogenesis and autophagy via regulation of the major nuclear export protein CRM-1.
abstract: Our previous work has shown that Akt3 is required for mitochondrial biogenesis in primary human endothelial cells (ECs) and in Akt3-null mice; Akt3 affects subcellular localization of peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1α), the master regulator of mitochondrial biogenesis. The purpose of this study is to determine the mechanism by which Akt3 controls the subcellular distribution of PGC-1α and to explore the effect on mitochondrial biogenesis and turnover during angiogenesis. Here we use standard biochemical analyses and Akt3-knockdown strategies to show that Akt3 controls the stabilization of chromosome maintenance region-1 (CRM-1), the major nuclear export receptor. Site-directed mutagenesis and association analyses show that PGC-1α nuclear export is CRM-1 dependent. Akt3 knockdown and CRM-1 overexpression cause 3-fold reductions in PGC-1α target gene expression, compared to control levels. Akt3 inhibition causes autophagy, as measured by autophagosome formation, in a CRM-1-dependent, Akt1/mTOR-independent pathway. In vivo, Akt3-null and heterozygous mice show dose-dependent decreases in angiogenesis compared to wild-type littermates (~5- and 2.5-fold decreases, respectively), as assessed by Matrigel plug assays. This correlates with an ~1.5-fold decrease in mitochondrial Cox IV expression. Our studies suggest that Akt3 is a regulator of mitochondrial dynamics in the vasculature via regulation of CRM-1-dependent nuclear export.
authors.affiliation: 1Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Ave, BSB654, Charleston, SC 29425, USA. musehelm@musc.edu.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Corum
authors.forename: Philip N
authors.initials: PN
authors.lastname: Tsichlis
authors.forename: Robin C
authors.initials: RC
authors.lastname: Muise-Helmericks
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics / Q000502:physiology*; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique; D061307:Human Umbilical Vein Endothelial Cells; D047468:Immunoprecipitation; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D063269:Mitochondrial Turnover / Q000235:genetics / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D028884:Karyopherins; D051057:Proto-Oncogene Proteins c-akt; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C491753:Akt3 protein, mouse
keywords: angiogenesis; endothelial cells; mitophagy